11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
28 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
29 #include "gc/shenandoah/shenandoahControlThread.hpp"
30 #include "gc/shenandoah/shenandoahDegeneratedGC.hpp"
31 #include "gc/shenandoah/shenandoahFreeSet.hpp"
32 #include "gc/shenandoah/shenandoahFullGC.hpp"
33 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
34 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
35 #include "gc/shenandoah/shenandoahMark.inline.hpp"
36 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
37 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
38 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
39 #include "gc/shenandoah/shenandoahUtils.hpp"
40 #include "gc/shenandoah/shenandoahVMOperations.hpp"
41 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
42 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
43 #include "memory/iterator.hpp"
44 #include "memory/metaspaceUtils.hpp"
45 #include "memory/metaspaceStats.hpp"
46 #include "memory/universe.hpp"
47 #include "runtime/atomic.hpp"
48
49 ShenandoahControlThread::ShenandoahControlThread() :
50 ConcurrentGCThread(),
51 _alloc_failure_waiters_lock(Mutex::safepoint-2, "ShenandoahAllocFailureGC_lock", true),
52 _gc_waiters_lock(Mutex::safepoint-2, "ShenandoahRequestedGC_lock", true),
53 _periodic_task(this),
54 _requested_gc_cause(GCCause::_no_cause_specified),
55 _degen_point(ShenandoahGC::_degenerated_outside_cycle),
56 _allocs_seen(0) {
57 set_name("Shenandoah Control Thread");
58 reset_gc_id();
59 create_and_start();
60 _periodic_task.enroll();
61 if (ShenandoahPacing) {
62 _periodic_pacer_notify_task.enroll();
63 }
64 }
65
66 ShenandoahControlThread::~ShenandoahControlThread() {
67 // This is here so that super is called.
68 }
69
70 void ShenandoahPeriodicTask::task() {
71 _thread->handle_force_counters_update();
72 _thread->handle_counters_update();
73 }
74
75 void ShenandoahPeriodicPacerNotify::task() {
76 assert(ShenandoahPacing, "Should not be here otherwise");
77 ShenandoahHeap::heap()->pacer()->notify_waiters();
78 }
79
80 void ShenandoahControlThread::run_service() {
81 ShenandoahHeap* heap = ShenandoahHeap::heap();
82
83 GCMode default_mode = concurrent_normal;
84 GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc;
85 int sleep = ShenandoahControlIntervalMin;
86
87 double last_shrink_time = os::elapsedTime();
88 double last_sleep_adjust_time = os::elapsedTime();
89
90 // Shrink period avoids constantly polling regions for shrinking.
91 // Having a period 10x lower than the delay would mean we hit the
92 // shrinking with lag of less than 1/10-th of true delay.
93 // ShenandoahUncommitDelay is in msecs, but shrink_period is in seconds.
94 double shrink_period = (double)ShenandoahUncommitDelay / 1000 / 10;
95
96 ShenandoahCollectorPolicy* policy = heap->shenandoah_policy();
97 ShenandoahHeuristics* heuristics = heap->heuristics();
98 while (!in_graceful_shutdown() && !should_terminate()) {
99 // Figure out if we have pending requests.
100 bool alloc_failure_pending = _alloc_failure_gc.is_set();
101 bool is_gc_requested = _gc_requested.is_set();
102 GCCause::Cause requested_gc_cause = _requested_gc_cause;
103 bool explicit_gc_requested = is_gc_requested && is_explicit_gc(requested_gc_cause);
104 bool implicit_gc_requested = is_gc_requested && !is_explicit_gc(requested_gc_cause);
105
106 // This control loop iteration have seen this much allocations.
107 size_t allocs_seen = Atomic::xchg(&_allocs_seen, (size_t)0, memory_order_relaxed);
108
109 // Check if we have seen a new target for soft max heap size.
110 bool soft_max_changed = check_soft_max_changed();
111
112 // Choose which GC mode to run in. The block below should select a single mode.
113 GCMode mode = none;
114 GCCause::Cause cause = GCCause::_last_gc_cause;
115 ShenandoahGC::ShenandoahDegenPoint degen_point = ShenandoahGC::_degenerated_unset;
116
117 if (alloc_failure_pending) {
118 // Allocation failure takes precedence: we have to deal with it first thing
119 log_info(gc)("Trigger: Handle Allocation Failure");
120
121 cause = GCCause::_allocation_failure;
122
123 // Consume the degen point, and seed it with default value
124 degen_point = _degen_point;
125 _degen_point = ShenandoahGC::_degenerated_outside_cycle;
126
127 if (ShenandoahDegeneratedGC && heuristics->should_degenerate_cycle()) {
128 heuristics->record_allocation_failure_gc();
129 policy->record_alloc_failure_to_degenerated(degen_point);
130 mode = stw_degenerated;
131 } else {
132 heuristics->record_allocation_failure_gc();
133 policy->record_alloc_failure_to_full();
134 mode = stw_full;
135 }
136
137 } else if (explicit_gc_requested) {
138 cause = requested_gc_cause;
139 log_info(gc)("Trigger: Explicit GC request (%s)", GCCause::to_string(cause));
140
141 heuristics->record_requested_gc();
142
143 if (ExplicitGCInvokesConcurrent) {
144 policy->record_explicit_to_concurrent();
145 mode = default_mode;
146 // Unload and clean up everything
147 heap->set_unload_classes(heuristics->can_unload_classes());
148 } else {
149 policy->record_explicit_to_full();
150 mode = stw_full;
151 }
152 } else if (implicit_gc_requested) {
153 cause = requested_gc_cause;
154 log_info(gc)("Trigger: Implicit GC request (%s)", GCCause::to_string(cause));
155
156 heuristics->record_requested_gc();
157
158 if (ShenandoahImplicitGCInvokesConcurrent) {
159 policy->record_implicit_to_concurrent();
160 mode = default_mode;
161
162 // Unload and clean up everything
163 heap->set_unload_classes(heuristics->can_unload_classes());
164 } else {
165 policy->record_implicit_to_full();
166 mode = stw_full;
167 }
168 } else {
169 // Potential normal cycle: ask heuristics if it wants to act
170 if (heuristics->should_start_gc()) {
171 mode = default_mode;
172 cause = default_cause;
173 }
174
175 // Ask policy if this cycle wants to process references or unload classes
176 heap->set_unload_classes(heuristics->should_unload_classes());
177 }
178
179 // Blow all soft references on this cycle, if handling allocation failure,
180 // either implicit or explicit GC request, or we are requested to do so unconditionally.
181 if (alloc_failure_pending || implicit_gc_requested || explicit_gc_requested || ShenandoahAlwaysClearSoftRefs) {
182 heap->soft_ref_policy()->set_should_clear_all_soft_refs(true);
183 }
184
185 bool gc_requested = (mode != none);
186 assert (!gc_requested || cause != GCCause::_last_gc_cause, "GC cause should be set");
187
188 if (gc_requested) {
189 // GC is starting, bump the internal ID
190 update_gc_id();
191
192 heap->reset_bytes_allocated_since_gc_start();
193
194 MetaspaceCombinedStats meta_sizes = MetaspaceUtils::get_combined_statistics();
195
196 // If GC was requested, we are sampling the counters even without actual triggers
197 // from allocation machinery. This captures GC phases more accurately.
198 set_forced_counters_update(true);
199
200 // If GC was requested, we better dump freeset data for performance debugging
201 {
202 ShenandoahHeapLocker locker(heap->lock());
203 heap->free_set()->log_status();
204 }
205
206 switch (mode) {
207 case concurrent_normal:
208 service_concurrent_normal_cycle(cause);
209 break;
210 case stw_degenerated:
211 service_stw_degenerated_cycle(cause, degen_point);
212 break;
213 case stw_full:
214 service_stw_full_cycle(cause);
215 break;
216 default:
217 ShouldNotReachHere();
218 }
219
220 // If this was the requested GC cycle, notify waiters about it
221 if (explicit_gc_requested || implicit_gc_requested) {
222 notify_gc_waiters();
223 }
224
225 // If this was the allocation failure GC cycle, notify waiters about it
226 if (alloc_failure_pending) {
227 notify_alloc_failure_waiters();
228 }
229
230 // Report current free set state at the end of cycle, whether
231 // it is a normal completion, or the abort.
232 {
233 ShenandoahHeapLocker locker(heap->lock());
234 heap->free_set()->log_status();
235
236 // Notify Universe about new heap usage. This has implications for
237 // global soft refs policy, and we better report it every time heap
238 // usage goes down.
239 Universe::heap()->update_capacity_and_used_at_gc();
240
241 // Signal that we have completed a visit to all live objects.
242 Universe::heap()->record_whole_heap_examined_timestamp();
243 }
244
245 // Disable forced counters update, and update counters one more time
246 // to capture the state at the end of GC session.
247 handle_force_counters_update();
248 set_forced_counters_update(false);
249
250 // Retract forceful part of soft refs policy
251 heap->soft_ref_policy()->set_should_clear_all_soft_refs(false);
252
253 // Clear metaspace oom flag, if current cycle unloaded classes
254 if (heap->unload_classes()) {
255 heuristics->clear_metaspace_oom();
256 }
257
258 // Commit worker statistics to cycle data
259 heap->phase_timings()->flush_par_workers_to_cycle();
260 if (ShenandoahPacing) {
261 heap->pacer()->flush_stats_to_cycle();
262 }
263
264 // Print GC stats for current cycle
265 {
266 LogTarget(Info, gc, stats) lt;
267 if (lt.is_enabled()) {
268 ResourceMark rm;
269 LogStream ls(lt);
270 heap->phase_timings()->print_cycle_on(&ls);
271 if (ShenandoahPacing) {
272 heap->pacer()->print_cycle_on(&ls);
273 }
274 }
275 }
276
277 // Commit statistics to globals
278 heap->phase_timings()->flush_cycle_to_global();
279
280 // Print Metaspace change following GC (if logging is enabled).
281 MetaspaceUtils::print_metaspace_change(meta_sizes);
282
283 // GC is over, we are at idle now
284 if (ShenandoahPacing) {
285 heap->pacer()->setup_for_idle();
286 }
287 } else {
288 // Allow allocators to know we have seen this much regions
289 if (ShenandoahPacing && (allocs_seen > 0)) {
290 heap->pacer()->report_alloc(allocs_seen);
291 }
292 }
293
294 double current = os::elapsedTime();
295
296 if (ShenandoahUncommit && (explicit_gc_requested || soft_max_changed || (current - last_shrink_time > shrink_period))) {
297 // Explicit GC tries to uncommit everything down to min capacity.
298 // Soft max change tries to uncommit everything down to target capacity.
299 // Periodic uncommit tries to uncommit suitable regions down to min capacity.
300
301 double shrink_before = (explicit_gc_requested || soft_max_changed) ?
302 current :
303 current - (ShenandoahUncommitDelay / 1000.0);
304
305 size_t shrink_until = soft_max_changed ?
306 heap->soft_max_capacity() :
307 heap->min_capacity();
308
309 service_uncommit(shrink_before, shrink_until);
310 heap->phase_timings()->flush_cycle_to_global();
311 last_shrink_time = current;
312 }
313
314 // Wait before performing the next action. If allocation happened during this wait,
315 // we exit sooner, to let heuristics re-evaluate new conditions. If we are at idle,
316 // back off exponentially.
317 if (_heap_changed.try_unset()) {
318 sleep = ShenandoahControlIntervalMin;
319 } else if ((current - last_sleep_adjust_time) * 1000 > ShenandoahControlIntervalAdjustPeriod){
320 sleep = MIN2<int>(ShenandoahControlIntervalMax, MAX2(1, sleep * 2));
321 last_sleep_adjust_time = current;
322 }
323 os::naked_short_sleep(sleep);
324 }
325
326 // Wait for the actual stop(), can't leave run_service() earlier.
327 while (!should_terminate()) {
328 os::naked_short_sleep(ShenandoahControlIntervalMin);
329 }
330 }
331
332 bool ShenandoahControlThread::check_soft_max_changed() const {
333 ShenandoahHeap* heap = ShenandoahHeap::heap();
334 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
335 size_t old_soft_max = heap->soft_max_capacity();
336 if (new_soft_max != old_soft_max) {
337 new_soft_max = MAX2(heap->min_capacity(), new_soft_max);
338 new_soft_max = MIN2(heap->max_capacity(), new_soft_max);
339 if (new_soft_max != old_soft_max) {
340 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
341 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
342 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
343 );
344 heap->set_soft_max_capacity(new_soft_max);
345 return true;
346 }
347 }
348 return false;
349 }
350
351 void ShenandoahControlThread::service_concurrent_normal_cycle(GCCause::Cause cause) {
352 // Normal cycle goes via all concurrent phases. If allocation failure (af) happens during
353 // any of the concurrent phases, it first degrades to Degenerated GC and completes GC there.
354 // If second allocation failure happens during Degenerated GC cycle (for example, when GC
355 // tries to evac something and no memory is available), cycle degrades to Full GC.
356 //
357 // There are also a shortcut through the normal cycle: immediate garbage shortcut, when
358 // heuristics says there are no regions to compact, and all the collection comes from immediately
359 // reclaimable regions.
360 //
361 // ................................................................................................
362 //
363 // (immediate garbage shortcut) Concurrent GC
364 // /-------------------------------------------\
365 // | |
366 // | |
367 // | |
368 // | v
369 // [START] ----> Conc Mark ----o----> Conc Evac --o--> Conc Update-Refs ---o----> [END]
370 // | | | ^
371 // | (af) | (af) | (af) |
372 // ..................|....................|.................|..............|.......................
373 // | | | |
374 // | | | | Degenerated GC
375 // v v v |
376 // STW Mark ----------> STW Evac ----> STW Update-Refs ----->o
377 // | | | ^
378 // | (af) | (af) | (af) |
379 // ..................|....................|.................|..............|.......................
380 // | | | |
381 // | v | | Full GC
382 // \------------------->o<----------------/ |
383 // | |
384 // v |
385 // Full GC --------------------------/
386 //
387 ShenandoahHeap* heap = ShenandoahHeap::heap();
388 if (check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle)) return;
389
390 GCIdMark gc_id_mark;
391 ShenandoahGCSession session(cause);
392
393 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
394
395 ShenandoahConcurrentGC gc;
396 if (gc.collect(cause)) {
397 // Cycle is complete
398 heap->heuristics()->record_success_concurrent();
399 heap->shenandoah_policy()->record_success_concurrent();
400 } else {
401 assert(heap->cancelled_gc(), "Must have been cancelled");
402 check_cancellation_or_degen(gc.degen_point());
403 }
404 }
405
406 bool ShenandoahControlThread::check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point) {
407 ShenandoahHeap* heap = ShenandoahHeap::heap();
408 if (heap->cancelled_gc()) {
409 assert (is_alloc_failure_gc() || in_graceful_shutdown(), "Cancel GC either for alloc failure GC, or gracefully exiting");
410 if (!in_graceful_shutdown()) {
411 assert (_degen_point == ShenandoahGC::_degenerated_outside_cycle,
412 "Should not be set yet: %s", ShenandoahGC::degen_point_to_string(_degen_point));
413 _degen_point = point;
414 }
415 return true;
416 }
417 return false;
418 }
419
420 void ShenandoahControlThread::stop_service() {
421 // Nothing to do here.
422 }
423
424 void ShenandoahControlThread::service_stw_full_cycle(GCCause::Cause cause) {
425 GCIdMark gc_id_mark;
426 ShenandoahGCSession session(cause);
427
428 ShenandoahFullGC gc;
429 gc.collect(cause);
430
431 ShenandoahHeap* const heap = ShenandoahHeap::heap();
432 heap->heuristics()->record_success_full();
433 heap->shenandoah_policy()->record_success_full();
434 }
435
436 void ShenandoahControlThread::service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point) {
437 assert (point != ShenandoahGC::_degenerated_unset, "Degenerated point should be set");
438
439 GCIdMark gc_id_mark;
440 ShenandoahGCSession session(cause);
441
442 ShenandoahDegenGC gc(point);
443 gc.collect(cause);
444
445 ShenandoahHeap* const heap = ShenandoahHeap::heap();
446 heap->heuristics()->record_success_degenerated();
447 heap->shenandoah_policy()->record_success_degenerated();
448 }
449
450 void ShenandoahControlThread::service_uncommit(double shrink_before, size_t shrink_until) {
451 ShenandoahHeap* heap = ShenandoahHeap::heap();
452
453 // Determine if there is work to do. This avoids taking heap lock if there is
454 // no work available, avoids spamming logs with superfluous logging messages,
455 // and minimises the amount of work while locks are taken.
456
457 if (heap->committed() <= shrink_until) return;
458
459 bool has_work = false;
460 for (size_t i = 0; i < heap->num_regions(); i++) {
461 ShenandoahHeapRegion *r = heap->get_region(i);
462 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
463 has_work = true;
464 break;
465 }
466 }
467
468 if (has_work) {
469 heap->entry_uncommit(shrink_before, shrink_until);
470 }
471 }
472
473 bool ShenandoahControlThread::is_explicit_gc(GCCause::Cause cause) const {
474 return GCCause::is_user_requested_gc(cause) ||
475 GCCause::is_serviceability_requested_gc(cause);
476 }
477
478 void ShenandoahControlThread::request_gc(GCCause::Cause cause) {
479 assert(GCCause::is_user_requested_gc(cause) ||
480 GCCause::is_serviceability_requested_gc(cause) ||
481 cause == GCCause::_metadata_GC_clear_soft_refs ||
482 cause == GCCause::_codecache_GC_aggressive ||
483 cause == GCCause::_codecache_GC_threshold ||
484 cause == GCCause::_full_gc_alot ||
485 cause == GCCause::_wb_young_gc ||
486 cause == GCCause::_wb_full_gc ||
487 cause == GCCause::_wb_breakpoint ||
488 cause == GCCause::_scavenge_alot,
489 "only requested GCs here: %s", GCCause::to_string(cause));
490
491 if (is_explicit_gc(cause)) {
492 if (!DisableExplicitGC) {
493 handle_requested_gc(cause);
494 }
495 } else {
496 handle_requested_gc(cause);
497 }
498 }
499
500 void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) {
501 // Make sure we have at least one complete GC cycle before unblocking
502 // from the explicit GC request.
503 //
504 // This is especially important for weak references cleanup and/or native
505 // resources (e.g. DirectByteBuffers) machinery: when explicit GC request
506 // comes very late in the already running cycle, it would miss lots of new
507 // opportunities for cleanup that were made available before the caller
508 // requested the GC.
509
510 MonitorLocker ml(&_gc_waiters_lock);
511 size_t current_gc_id = get_gc_id();
512 size_t required_gc_id = current_gc_id + 1;
513 while (current_gc_id < required_gc_id) {
514 // Although setting gc request is under _gc_waiters_lock, but read side (run_service())
515 // does not take the lock. We need to enforce following order, so that read side sees
516 // latest requested gc cause when the flag is set.
517 _requested_gc_cause = cause;
518 _gc_requested.set();
519
520 if (cause != GCCause::_wb_breakpoint) {
521 ml.wait();
522 }
523 current_gc_id = get_gc_id();
524 }
525 }
526
527 void ShenandoahControlThread::handle_alloc_failure(ShenandoahAllocRequest& req) {
528 ShenandoahHeap* heap = ShenandoahHeap::heap();
529
530 assert(current()->is_Java_thread(), "expect Java thread here");
531
532 if (try_set_alloc_failure_gc()) {
533 // Only report the first allocation failure
534 log_info(gc)("Failed to allocate %s, " SIZE_FORMAT "%s",
535 req.type_string(),
536 byte_size_in_proper_unit(req.size() * HeapWordSize), proper_unit_for_byte_size(req.size() * HeapWordSize));
537
538 // Now that alloc failure GC is scheduled, we can abort everything else
539 heap->cancel_gc(GCCause::_allocation_failure);
583 _do_counters_update.unset();
584 ShenandoahHeap::heap()->monitoring_support()->update_counters();
585 }
586 }
587
588 void ShenandoahControlThread::handle_force_counters_update() {
589 if (_force_counters_update.is_set()) {
590 _do_counters_update.unset(); // reset these too, we do update now!
591 ShenandoahHeap::heap()->monitoring_support()->update_counters();
592 }
593 }
594
595 void ShenandoahControlThread::notify_heap_changed() {
596 // This is called from allocation path, and thus should be fast.
597
598 // Update monitoring counters when we took a new region. This amortizes the
599 // update costs on slow path.
600 if (_do_counters_update.is_unset()) {
601 _do_counters_update.set();
602 }
603 // Notify that something had changed.
604 if (_heap_changed.is_unset()) {
605 _heap_changed.set();
606 }
607 }
608
609 void ShenandoahControlThread::pacing_notify_alloc(size_t words) {
610 assert(ShenandoahPacing, "should only call when pacing is enabled");
611 Atomic::add(&_allocs_seen, words, memory_order_relaxed);
612 }
613
614 void ShenandoahControlThread::set_forced_counters_update(bool value) {
615 _force_counters_update.set_cond(value);
616 }
617
618 void ShenandoahControlThread::reset_gc_id() {
619 Atomic::store(&_gc_id, (size_t)0);
620 }
621
622 void ShenandoahControlThread::update_gc_id() {
623 Atomic::inc(&_gc_id);
624 }
625
626 size_t ShenandoahControlThread::get_gc_id() {
627 return Atomic::load(&_gc_id);
628 }
629
630 void ShenandoahControlThread::start() {
631 create_and_start();
632 }
633
634 void ShenandoahControlThread::prepare_for_graceful_shutdown() {
635 _graceful_shutdown.set();
636 }
637
638 bool ShenandoahControlThread::in_graceful_shutdown() {
639 return _graceful_shutdown.is_set();
640 }
|
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
28 #include "gc/shenandoah/shenandoahConcurrentGC.hpp"
29 #include "gc/shenandoah/shenandoahControlThread.hpp"
30 #include "gc/shenandoah/shenandoahDegeneratedGC.hpp"
31 #include "gc/shenandoah/shenandoahEvacTracker.hpp"
32 #include "gc/shenandoah/shenandoahFreeSet.hpp"
33 #include "gc/shenandoah/shenandoahFullGC.hpp"
34 #include "gc/shenandoah/shenandoahGeneration.hpp"
35 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
36 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
37 #include "gc/shenandoah/shenandoahPhaseTimings.hpp"
38 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
39 #include "gc/shenandoah/shenandoahMark.inline.hpp"
40 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
41 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
42 #include "gc/shenandoah/shenandoahOldGC.hpp"
43 #include "gc/shenandoah/shenandoahRootProcessor.inline.hpp"
44 #include "gc/shenandoah/shenandoahUtils.hpp"
45 #include "gc/shenandoah/shenandoahVMOperations.hpp"
46 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
47 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
48 #include "gc/shenandoah/mode/shenandoahMode.hpp"
49 #include "memory/iterator.hpp"
50 #include "memory/metaspaceUtils.hpp"
51 #include "memory/metaspaceStats.hpp"
52 #include "memory/universe.hpp"
53 #include "runtime/atomic.hpp"
54
55 ShenandoahControlThread::ShenandoahControlThread() :
56 ConcurrentGCThread(),
57 _alloc_failure_waiters_lock(Mutex::safepoint - 2, "ShenandoahAllocFailureGC_lock", true),
58 _gc_waiters_lock(Mutex::safepoint - 2, "ShenandoahRequestedGC_lock", true),
59 _control_lock(Mutex::nosafepoint - 2, "ShenandoahControlGC_lock", true),
60 _regulator_lock(Mutex::nosafepoint - 2, "ShenandoahRegulatorGC_lock", true),
61 _periodic_task(this),
62 _requested_gc_cause(GCCause::_no_cause_specified),
63 _requested_generation(GenerationMode::GLOBAL),
64 _degen_point(ShenandoahGC::_degenerated_outside_cycle),
65 _degen_generation(NULL),
66 _allocs_seen(0),
67 _mode(none) {
68 set_name("Shenandoah Control Thread");
69 reset_gc_id();
70 create_and_start();
71 _periodic_task.enroll();
72 if (ShenandoahPacing) {
73 _periodic_pacer_notify_task.enroll();
74 }
75 }
76
77 ShenandoahControlThread::~ShenandoahControlThread() {
78 // This is here so that super is called.
79 }
80
81 void ShenandoahPeriodicTask::task() {
82 _thread->handle_force_counters_update();
83 _thread->handle_counters_update();
84 }
85
86 void ShenandoahPeriodicPacerNotify::task() {
87 assert(ShenandoahPacing, "Should not be here otherwise");
88 ShenandoahHeap::heap()->pacer()->notify_waiters();
89 }
90
91 void ShenandoahControlThread::run_service() {
92 ShenandoahHeap* heap = ShenandoahHeap::heap();
93
94 GCMode default_mode = concurrent_normal;
95 GenerationMode generation = GLOBAL;
96 GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc;
97
98 double last_shrink_time = os::elapsedTime();
99 uint age_period = 0;
100
101 // Shrink period avoids constantly polling regions for shrinking.
102 // Having a period 10x lower than the delay would mean we hit the
103 // shrinking with lag of less than 1/10-th of true delay.
104 // ShenandoahUncommitDelay is in msecs, but shrink_period is in seconds.
105 double shrink_period = (double)ShenandoahUncommitDelay / 1000 / 10;
106
107 ShenandoahCollectorPolicy* policy = heap->shenandoah_policy();
108
109 // Heuristics are notified of allocation failures here and other outcomes
110 // of the cycle. They're also used here to control whether the Nth consecutive
111 // degenerated cycle should be 'promoted' to a full cycle. The decision to
112 // trigger a cycle or not is evaluated on the regulator thread.
113 ShenandoahHeuristics* global_heuristics = heap->global_generation()->heuristics();
114 while (!in_graceful_shutdown() && !should_terminate()) {
115 // Figure out if we have pending requests.
116 bool alloc_failure_pending = _alloc_failure_gc.is_set();
117 bool is_gc_requested = _gc_requested.is_set();
118 GCCause::Cause requested_gc_cause = _requested_gc_cause;
119 bool explicit_gc_requested = is_gc_requested && is_explicit_gc(requested_gc_cause);
120 bool implicit_gc_requested = is_gc_requested && is_implicit_gc(requested_gc_cause);
121
122 // This control loop iteration have seen this much allocations.
123 size_t allocs_seen = Atomic::xchg(&_allocs_seen, (size_t)0, memory_order_relaxed);
124
125 // Check if we have seen a new target for soft max heap size.
126 bool soft_max_changed = check_soft_max_changed();
127
128 // Choose which GC mode to run in. The block below should select a single mode.
129 set_gc_mode(none);
130 GCCause::Cause cause = GCCause::_last_gc_cause;
131 ShenandoahGC::ShenandoahDegenPoint degen_point = ShenandoahGC::_degenerated_unset;
132
133 if (alloc_failure_pending) {
134 // Allocation failure takes precedence: we have to deal with it first thing
135 log_info(gc)("Trigger: Handle Allocation Failure");
136
137 cause = GCCause::_allocation_failure;
138
139 // Consume the degen point, and seed it with default value
140 degen_point = _degen_point;
141 _degen_point = ShenandoahGC::_degenerated_outside_cycle;
142
143 if (degen_point == ShenandoahGC::_degenerated_outside_cycle) {
144 _degen_generation = heap->mode()->is_generational() ? heap->young_generation() : heap->global_generation();
145 } else {
146 assert(_degen_generation != NULL, "Need to know which generation to resume.");
147 }
148
149 ShenandoahHeuristics* heuristics = _degen_generation->heuristics();
150 generation = _degen_generation->generation_mode();
151 bool old_gen_evacuation_failed = heap->clear_old_evacuation_failure();
152
153 // Do not bother with degenerated cycle if old generation evacuation failed.
154 if (ShenandoahDegeneratedGC && heuristics->should_degenerate_cycle() && !old_gen_evacuation_failed) {
155 heuristics->record_allocation_failure_gc();
156 policy->record_alloc_failure_to_degenerated(degen_point);
157 set_gc_mode(stw_degenerated);
158 } else {
159 heuristics->record_allocation_failure_gc();
160 policy->record_alloc_failure_to_full();
161 generation = GLOBAL;
162 set_gc_mode(stw_full);
163 }
164 } else if (explicit_gc_requested) {
165 cause = requested_gc_cause;
166 generation = GLOBAL;
167 log_info(gc)("Trigger: Explicit GC request (%s)", GCCause::to_string(cause));
168
169 global_heuristics->record_requested_gc();
170
171 if (ExplicitGCInvokesConcurrent) {
172 policy->record_explicit_to_concurrent();
173 set_gc_mode(default_mode);
174 // Unload and clean up everything
175 heap->set_unload_classes(global_heuristics->can_unload_classes());
176 } else {
177 policy->record_explicit_to_full();
178 set_gc_mode(stw_full);
179 }
180 } else if (implicit_gc_requested) {
181 cause = requested_gc_cause;
182 generation = GLOBAL;
183 log_info(gc)("Trigger: Implicit GC request (%s)", GCCause::to_string(cause));
184
185 global_heuristics->record_requested_gc();
186
187 if (ShenandoahImplicitGCInvokesConcurrent) {
188 policy->record_implicit_to_concurrent();
189 set_gc_mode(default_mode);
190
191 // Unload and clean up everything
192 heap->set_unload_classes(global_heuristics->can_unload_classes());
193 } else {
194 policy->record_implicit_to_full();
195 set_gc_mode(stw_full);
196 }
197 } else {
198 // We should only be here if the regulator requested a cycle or if
199 // there is an old generation mark in progress.
200 if (_requested_gc_cause == GCCause::_shenandoah_concurrent_gc) {
201 if (_requested_generation == OLD && heap->doing_mixed_evacuations()) {
202 // If a request to start an old cycle arrived while an old cycle was running, but _before_
203 // it chose any regions for evacuation we don't want to start a new old cycle. Rather, we want
204 // the heuristic to run a young collection so that we can evacuate some old regions.
205 assert(!heap->is_concurrent_old_mark_in_progress(), "Should not be running mixed collections and concurrent marking.");
206 generation = YOUNG;
207 } else {
208 generation = _requested_generation;
209 }
210
211 // preemption was requested or this is a regular cycle
212 cause = GCCause::_shenandoah_concurrent_gc;
213 set_gc_mode(default_mode);
214
215 // Don't start a new old marking if there is one already in progress.
216 if (generation == OLD && heap->is_concurrent_old_mark_in_progress()) {
217 set_gc_mode(servicing_old);
218 }
219
220 if (generation == GLOBAL) {
221 heap->set_unload_classes(global_heuristics->should_unload_classes());
222 } else {
223 heap->set_unload_classes(false);
224 }
225
226 // Don't want to spin in this loop and start a cycle every time, so
227 // clear requested gc cause. This creates a race with callers of the
228 // blocking 'request_gc' method, but there it loops and resets the
229 // '_requested_gc_cause' until a full cycle is completed.
230 _requested_gc_cause = GCCause::_no_gc;
231 } else if (heap->is_concurrent_old_mark_in_progress() || heap->is_prepare_for_old_mark_in_progress()) {
232 // Nobody asked us to do anything, but we have an old-generation mark or old-generation preparation for
233 // mixed evacuation in progress, so resume working on that.
234 log_info(gc)("Resume old gc: marking=%s, preparing=%s",
235 BOOL_TO_STR(heap->is_concurrent_old_mark_in_progress()),
236 BOOL_TO_STR(heap->is_prepare_for_old_mark_in_progress()));
237
238 cause = GCCause::_shenandoah_concurrent_gc;
239 generation = OLD;
240 set_gc_mode(servicing_old);
241 }
242 }
243
244 // Blow all soft references on this cycle, if handling allocation failure,
245 // either implicit or explicit GC request, or we are requested to do so unconditionally.
246 if (generation == GLOBAL && (alloc_failure_pending || implicit_gc_requested || explicit_gc_requested || ShenandoahAlwaysClearSoftRefs)) {
247 heap->soft_ref_policy()->set_should_clear_all_soft_refs(true);
248 }
249
250 bool gc_requested = (_mode != none);
251 assert (!gc_requested || cause != GCCause::_last_gc_cause, "GC cause should be set");
252
253 if (gc_requested) {
254 // GC is starting, bump the internal ID
255 update_gc_id();
256
257 heap->reset_bytes_allocated_since_gc_start();
258
259 MetaspaceCombinedStats meta_sizes = MetaspaceUtils::get_combined_statistics();
260
261 // If GC was requested, we are sampling the counters even without actual triggers
262 // from allocation machinery. This captures GC phases more accurately.
263 set_forced_counters_update(true);
264
265 // If GC was requested, we better dump freeset data for performance debugging
266 {
267 ShenandoahHeapLocker locker(heap->lock());
268 heap->free_set()->log_status();
269 }
270
271 heap->set_aging_cycle(false);
272 {
273 switch (_mode) {
274 case concurrent_normal: {
275 if ((generation == YOUNG) && (age_period-- == 0)) {
276 heap->set_aging_cycle(true);
277 age_period = ShenandoahAgingCyclePeriod - 1;
278 }
279 service_concurrent_normal_cycle(heap, generation, cause);
280 break;
281 }
282 case stw_degenerated: {
283 if (!service_stw_degenerated_cycle(cause, degen_point)) {
284 // The degenerated GC was upgraded to a Full GC
285 generation = GLOBAL;
286 }
287 break;
288 }
289 case stw_full: {
290 service_stw_full_cycle(cause);
291 break;
292 }
293 case servicing_old: {
294 assert(generation == OLD, "Expected old generation here");
295 GCIdMark gc_id_mark;
296 service_concurrent_old_cycle(heap, cause);
297 break;
298 }
299 default: {
300 ShouldNotReachHere();
301 }
302 }
303 }
304
305 // If this was the requested GC cycle, notify waiters about it
306 if (explicit_gc_requested || implicit_gc_requested) {
307 notify_gc_waiters();
308 }
309
310 // If this was the allocation failure GC cycle, notify waiters about it
311 if (alloc_failure_pending) {
312 notify_alloc_failure_waiters();
313 }
314
315 // Report current free set state at the end of cycle, whether
316 // it is a normal completion, or the abort.
317 {
318 ShenandoahHeapLocker locker(heap->lock());
319 heap->free_set()->log_status();
320
321 // Notify Universe about new heap usage. This has implications for
322 // global soft refs policy, and we better report it every time heap
323 // usage goes down.
324 Universe::heap()->update_capacity_and_used_at_gc();
325
326 // Signal that we have completed a visit to all live objects.
327 Universe::heap()->record_whole_heap_examined_timestamp();
328 }
329
330 // Disable forced counters update, and update counters one more time
331 // to capture the state at the end of GC session.
332 handle_force_counters_update();
333 set_forced_counters_update(false);
334
335 // Retract forceful part of soft refs policy
336 heap->soft_ref_policy()->set_should_clear_all_soft_refs(false);
337
338 // Clear metaspace oom flag, if current cycle unloaded classes
339 if (heap->unload_classes()) {
340 assert(generation == GLOBAL, "Only unload classes during GLOBAL cycle");
341 global_heuristics->clear_metaspace_oom();
342 }
343
344 process_phase_timings(heap);
345
346 // Print Metaspace change following GC (if logging is enabled).
347 MetaspaceUtils::print_metaspace_change(meta_sizes);
348
349 // GC is over, we are at idle now
350 if (ShenandoahPacing) {
351 heap->pacer()->setup_for_idle();
352 }
353 } else {
354 // Allow allocators to know we have seen this much regions
355 if (ShenandoahPacing && (allocs_seen > 0)) {
356 heap->pacer()->report_alloc(allocs_seen);
357 }
358 }
359
360 double current = os::elapsedTime();
361
362 if (ShenandoahUncommit && (explicit_gc_requested || soft_max_changed || (current - last_shrink_time > shrink_period))) {
363 // Explicit GC tries to uncommit everything down to min capacity.
364 // Soft max change tries to uncommit everything down to target capacity.
365 // Periodic uncommit tries to uncommit suitable regions down to min capacity.
366
367 double shrink_before = (explicit_gc_requested || soft_max_changed) ?
368 current :
369 current - (ShenandoahUncommitDelay / 1000.0);
370
371 size_t shrink_until = soft_max_changed ?
372 heap->soft_max_capacity() :
373 heap->min_capacity();
374
375 service_uncommit(shrink_before, shrink_until);
376 heap->phase_timings()->flush_cycle_to_global();
377 last_shrink_time = current;
378 }
379
380 // Don't wait around if there was an allocation failure - start the next cycle immediately.
381 if (!is_alloc_failure_gc()) {
382 // The timed wait is necessary because this thread has a responsibility to send
383 // 'alloc_words' to the pacer when it does not perform a GC.
384 MonitorLocker lock(&_control_lock, Mutex::_no_safepoint_check_flag);
385 lock.wait(ShenandoahControlIntervalMax);
386 }
387 }
388
389 // Wait for the actual stop(), can't leave run_service() earlier.
390 while (!should_terminate()) {
391 os::naked_short_sleep(ShenandoahControlIntervalMin);
392 }
393 }
394
395 void ShenandoahControlThread::process_phase_timings(const ShenandoahHeap* heap) {
396
397 // Commit worker statistics to cycle data
398 heap->phase_timings()->flush_par_workers_to_cycle();
399 if (ShenandoahPacing) {
400 heap->pacer()->flush_stats_to_cycle();
401 }
402
403 ShenandoahCycleStats evac_stats = heap->evac_tracker()->flush_cycle_to_global();
404
405 // Print GC stats for current cycle
406 {
407 LogTarget(Info, gc, stats) lt;
408 if (lt.is_enabled()) {
409 ResourceMark rm;
410 LogStream ls(lt);
411 heap->phase_timings()->print_cycle_on(&ls);
412 ShenandoahEvacuationTracker::print_evacuations_on(&ls, &evac_stats.workers,
413 &evac_stats.mutators);
414 if (ShenandoahPacing) {
415 heap->pacer()->print_cycle_on(&ls);
416 }
417 }
418 }
419
420 // Commit statistics to globals
421 heap->phase_timings()->flush_cycle_to_global();
422
423 }
424
425 // Young and old concurrent cycles are initiated by the regulator. Implicit
426 // and explicit GC requests are handled by the controller thread and always
427 // run a global cycle (which is concurrent by default, but may be overridden
428 // by command line options). Old cycles always degenerate to a global cycle.
429 // Young cycles are degenerated to complete the young cycle. Young
430 // and old degen may upgrade to Full GC. Full GC may also be
431 // triggered directly by a System.gc() invocation.
432 //
433 //
434 // +-----+ Idle +-----+-----------+---------------------+
435 // | + | | |
436 // | | | | |
437 // | | v | |
438 // | | Bootstrap Old +-- | ------------+ |
439 // | | + | | |
440 // | | | | | |
441 // | v v v v |
442 // | Resume Old <----------+ Young +--> Young Degen |
443 // | + + ^ + + |
444 // v | | | | | |
445 // Global <-+ | +----------------------------+ | |
446 // + | | |
447 // | v v |
448 // +---> Global Degen +--------------------> Full <----+
449 //
450 void ShenandoahControlThread::service_concurrent_normal_cycle(
451 const ShenandoahHeap* heap, const GenerationMode generation, GCCause::Cause cause) {
452 GCIdMark gc_id_mark;
453 switch (generation) {
454 case YOUNG: {
455 // Run a young cycle. This might or might not, have interrupted an ongoing
456 // concurrent mark in the old generation. We need to think about promotions
457 // in this case. Promoted objects should be above the TAMS in the old regions
458 // they end up in, but we have to be sure we don't promote into any regions
459 // that are in the cset.
460 log_info(gc, ergo)("Start GC cycle (YOUNG)");
461 service_concurrent_cycle(heap->young_generation(), cause, false);
462 break;
463 }
464 case GLOBAL: {
465 log_info(gc, ergo)("Start GC cycle (GLOBAL)");
466 service_concurrent_cycle(heap->global_generation(), cause, false);
467 break;
468 }
469 case OLD: {
470 log_info(gc, ergo)("Start GC cycle (OLD)");
471 service_concurrent_old_cycle(heap, cause);
472 break;
473 }
474 default:
475 ShouldNotReachHere();
476 }
477 const char* msg;
478 if (heap->cancelled_gc()) {
479 msg = (generation == YOUNG)? "At end of Interrupted Concurrent Young GC": "At end of Interrupted Concurrent Bootstrap GC";
480 } else {
481 msg = (generation == YOUNG)? "At end of Concurrent Young GC": "At end of Concurrent Bootstrap GC";
482 }
483 heap->log_heap_status(msg);
484 }
485
486 void ShenandoahControlThread::service_concurrent_old_cycle(const ShenandoahHeap* heap, GCCause::Cause &cause) {
487
488 ShenandoahOldGeneration* old_generation = heap->old_generation();
489 ShenandoahYoungGeneration* young_generation = heap->young_generation();
490 ShenandoahOldGeneration::State original_state = old_generation->state();
491
492 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
493
494 switch (original_state) {
495 case ShenandoahOldGeneration::IDLE: {
496 assert(!heap->is_concurrent_old_mark_in_progress(), "Old already in progress.");
497 assert(old_generation->task_queues()->is_empty(), "Old mark queues should be empty.");
498 }
499 case ShenandoahOldGeneration::FILLING: {
500 _allow_old_preemption.set();
501 ShenandoahGCSession session(cause, old_generation);
502 old_generation->prepare_gc();
503 _allow_old_preemption.unset();
504
505 if (heap->is_prepare_for_old_mark_in_progress()) {
506 assert(old_generation->state() == ShenandoahOldGeneration::FILLING, "Prepare for mark should be in progress.");
507 return;
508 }
509
510 assert(old_generation->state() == ShenandoahOldGeneration::BOOTSTRAPPING, "Finished with filling, should be bootstrapping.");
511 }
512 case ShenandoahOldGeneration::BOOTSTRAPPING: {
513 // Configure the young generation's concurrent mark to put objects in
514 // old regions into the concurrent mark queues associated with the old
515 // generation. The young cycle will run as normal except that rather than
516 // ignore old references it will mark and enqueue them in the old concurrent
517 // task queues but it will not traverse them.
518 young_generation->set_old_gen_task_queues(old_generation->task_queues());
519 ShenandoahGCSession session(cause, young_generation);
520 service_concurrent_cycle(heap,young_generation, cause, true);
521 process_phase_timings(heap);
522 if (heap->cancelled_gc()) {
523 // Young generation bootstrap cycle has failed. Concurrent mark for old generation
524 // is going to resume after degenerated bootstrap cycle completes.
525 log_info(gc)("Bootstrap cycle for old generation was cancelled.");
526 return;
527 }
528
529 // Reset the degenerated point. Normally this would happen at the top
530 // of the control loop, but here we have just completed a young cycle
531 // which has bootstrapped the old concurrent marking.
532 _degen_point = ShenandoahGC::_degenerated_outside_cycle;
533
534 // From here we will 'resume' the old concurrent mark. This will skip reset
535 // and init mark for the concurrent mark. All of that work will have been
536 // done by the bootstrapping young cycle. In order to simplify the debugging
537 // effort, the old cycle will ONLY complete the mark phase. No actual
538 // collection of the old generation is happening here.
539 set_gc_mode(servicing_old);
540 old_generation->transition_to(ShenandoahOldGeneration::MARKING);
541 }
542 case ShenandoahOldGeneration::MARKING: {
543 ShenandoahGCSession session(cause, old_generation);
544 bool marking_complete = resume_concurrent_old_cycle(old_generation, cause);
545 if (marking_complete) {
546 assert(old_generation->state() != ShenandoahOldGeneration::MARKING, "Should not still be marking.");
547 if (original_state == ShenandoahOldGeneration::MARKING) {
548 heap->log_heap_status("At end of Concurrent Old Marking finishing increment");
549 }
550 } else if (original_state == ShenandoahOldGeneration::MARKING) {
551 heap->log_heap_status("At end of Concurrent Old Marking increment");
552 }
553 break;
554 }
555 default:
556 log_error(gc)("Unexpected state for old GC: %d", old_generation->state());
557 ShouldNotReachHere();
558 }
559 }
560
561 bool ShenandoahControlThread::resume_concurrent_old_cycle(ShenandoahGeneration* generation, GCCause::Cause cause) {
562
563 assert(ShenandoahHeap::heap()->is_concurrent_old_mark_in_progress(), "Old mark should be in progress");
564 log_debug(gc)("Resuming old generation with " UINT32_FORMAT " marking tasks queued.", generation->task_queues()->tasks());
565
566 ShenandoahHeap* heap = ShenandoahHeap::heap();
567
568 // We can only tolerate being cancelled during concurrent marking or during preparation for mixed
569 // evacuation. This flag here (passed by reference) is used to control precisely where the regulator
570 // is allowed to cancel a GC.
571 ShenandoahOldGC gc(generation, _allow_old_preemption);
572 if (gc.collect(cause)) {
573 generation->record_success_concurrent(false);
574 }
575
576 if (heap->cancelled_gc()) {
577 // It's possible the gc cycle was cancelled after the last time
578 // the collection checked for cancellation. In which case, the
579 // old gc cycle is still completed, and we have to deal with this
580 // cancellation. We set the degeneration point to be outside
581 // the cycle because if this is an allocation failure, that is
582 // what must be done (there is no degenerated old cycle). If the
583 // cancellation was due to a heuristic wanting to start a young
584 // cycle, then we are not actually going to a degenerated cycle,
585 // so the degenerated point doesn't matter here.
586 check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle);
587 if (_requested_gc_cause == GCCause::_shenandoah_concurrent_gc) {
588 heap->shenandoah_policy()->record_interrupted_old();
589 }
590 return false;
591 }
592 return true;
593 }
594
595 bool ShenandoahControlThread::check_soft_max_changed() const {
596 ShenandoahHeap* heap = ShenandoahHeap::heap();
597 size_t new_soft_max = Atomic::load(&SoftMaxHeapSize);
598 size_t old_soft_max = heap->soft_max_capacity();
599 if (new_soft_max != old_soft_max) {
600 new_soft_max = MAX2(heap->min_capacity(), new_soft_max);
601 new_soft_max = MIN2(heap->max_capacity(), new_soft_max);
602 if (new_soft_max != old_soft_max) {
603 log_info(gc)("Soft Max Heap Size: " SIZE_FORMAT "%s -> " SIZE_FORMAT "%s",
604 byte_size_in_proper_unit(old_soft_max), proper_unit_for_byte_size(old_soft_max),
605 byte_size_in_proper_unit(new_soft_max), proper_unit_for_byte_size(new_soft_max)
606 );
607 heap->set_soft_max_capacity(new_soft_max);
608 return true;
609 }
610 }
611 return false;
612 }
613
614 void ShenandoahControlThread::service_concurrent_cycle(ShenandoahGeneration* generation, GCCause::Cause cause, bool do_old_gc_bootstrap) {
615 // Normal cycle goes via all concurrent phases. If allocation failure (af) happens during
616 // any of the concurrent phases, it first degrades to Degenerated GC and completes GC there.
617 // If second allocation failure happens during Degenerated GC cycle (for example, when GC
618 // tries to evac something and no memory is available), cycle degrades to Full GC.
619 //
620 // There are also a shortcut through the normal cycle: immediate garbage shortcut, when
621 // heuristics says there are no regions to compact, and all the collection comes from immediately
622 // reclaimable regions.
623 //
624 // ................................................................................................
625 //
626 // (immediate garbage shortcut) Concurrent GC
627 // /-------------------------------------------\
628 // | |
629 // | |
630 // | |
631 // | v
632 // [START] ----> Conc Mark ----o----> Conc Evac --o--> Conc Update-Refs ---o----> [END]
633 // | | | ^
634 // | (af) | (af) | (af) |
635 // ..................|....................|.................|..............|.......................
636 // | | | |
637 // | | | | Degenerated GC
638 // v v v |
639 // STW Mark ----------> STW Evac ----> STW Update-Refs ----->o
640 // | | | ^
641 // | (af) | (af) | (af) |
642 // ..................|....................|.................|..............|.......................
643 // | | | |
644 // | v | | Full GC
645 // \------------------->o<----------------/ |
646 // | |
647 // v |
648 // Full GC --------------------------/
649 //
650 if (check_cancellation_or_degen(ShenandoahGC::_degenerated_outside_cycle)) return;
651
652 ShenandoahHeap* heap = ShenandoahHeap::heap();
653 ShenandoahGCSession session(cause, generation);
654 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
655
656 service_concurrent_cycle(heap, generation, cause, do_old_gc_bootstrap);
657 }
658
659 void ShenandoahControlThread::service_concurrent_cycle(const ShenandoahHeap* heap, ShenandoahGeneration* generation,
660 GCCause::Cause &cause, bool do_old_gc_bootstrap) {
661 ShenandoahConcurrentGC gc(generation, do_old_gc_bootstrap);
662 if (gc.collect(cause)) {
663 // Cycle is complete
664 generation->record_success_concurrent(gc.abbreviated());
665 } else {
666 assert(heap->cancelled_gc(), "Must have been cancelled");
667 check_cancellation_or_degen(gc.degen_point());
668 assert(generation->generation_mode() != OLD, "Old GC takes a different control path");
669 // Concurrent young-gen collection degenerates to young
670 // collection. Same for global collections.
671 _degen_generation = generation;
672 }
673 }
674
675 bool ShenandoahControlThread::check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point) {
676 ShenandoahHeap* heap = ShenandoahHeap::heap();
677 if (!heap->cancelled_gc()) {
678 return false;
679 }
680
681 if (in_graceful_shutdown()) {
682 return true;
683 }
684
685 assert(_degen_point == ShenandoahGC::_degenerated_outside_cycle,
686 "Should not be set yet: %s", ShenandoahGC::degen_point_to_string(_degen_point));
687
688 if (is_alloc_failure_gc()) {
689 _degen_point = point;
690 return true;
691 }
692
693 if (_preemption_requested.is_set()) {
694 assert(_requested_generation == YOUNG, "Only young GCs may preempt old.");
695 _preemption_requested.unset();
696
697 // Old generation marking is only cancellable during concurrent marking.
698 // Once final mark is complete, the code does not check again for cancellation.
699 // If old generation was cancelled for an allocation failure, we wouldn't
700 // make it to this case. The calling code is responsible for forcing a
701 // cancellation due to allocation failure into a degenerated cycle.
702 _degen_point = point;
703 heap->clear_cancelled_gc(false /* clear oom handler */);
704 return true;
705 }
706
707 fatal("Cancel GC either for alloc failure GC, or gracefully exiting, or to pause old generation marking.");
708 return false;
709 }
710
711 void ShenandoahControlThread::stop_service() {
712 // Nothing to do here.
713 }
714
715 void ShenandoahControlThread::service_stw_full_cycle(GCCause::Cause cause) {
716 ShenandoahHeap* const heap = ShenandoahHeap::heap();
717
718 GCIdMark gc_id_mark;
719 ShenandoahGCSession session(cause, heap->global_generation());
720
721 ShenandoahFullGC gc;
722 gc.collect(cause);
723
724 heap->global_generation()->heuristics()->record_success_full();
725 heap->shenandoah_policy()->record_success_full();
726 }
727
728 bool ShenandoahControlThread::service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point) {
729 assert (point != ShenandoahGC::_degenerated_unset, "Degenerated point should be set");
730 ShenandoahHeap* const heap = ShenandoahHeap::heap();
731
732 GCIdMark gc_id_mark;
733 ShenandoahGCSession session(cause, _degen_generation);
734
735 ShenandoahDegenGC gc(point, _degen_generation);
736 gc.collect(cause);
737
738 assert(heap->young_generation()->task_queues()->is_empty(), "Unexpected young generation marking tasks");
739 if (_degen_generation->generation_mode() == GLOBAL) {
740 assert(heap->old_generation()->task_queues()->is_empty(), "Unexpected old generation marking tasks");
741 assert(heap->global_generation()->task_queues()->is_empty(), "Unexpected global generation marking tasks");
742 } else {
743 assert(_degen_generation->generation_mode() == YOUNG, "Expected degenerated young cycle, if not global.");
744 ShenandoahOldGeneration* old_generation = (ShenandoahOldGeneration*) heap->old_generation();
745 if (old_generation->state() == ShenandoahOldGeneration::BOOTSTRAPPING && !gc.upgraded_to_full()) {
746 old_generation->transition_to(ShenandoahOldGeneration::MARKING);
747 }
748 }
749
750 _degen_generation->heuristics()->record_success_degenerated();
751 heap->shenandoah_policy()->record_success_degenerated();
752 return !gc.upgraded_to_full();
753 }
754
755 void ShenandoahControlThread::service_uncommit(double shrink_before, size_t shrink_until) {
756 ShenandoahHeap* heap = ShenandoahHeap::heap();
757
758 // Determine if there is work to do. This avoids taking heap lock if there is
759 // no work available, avoids spamming logs with superfluous logging messages,
760 // and minimises the amount of work while locks are taken.
761
762 if (heap->committed() <= shrink_until) return;
763
764 bool has_work = false;
765 for (size_t i = 0; i < heap->num_regions(); i++) {
766 ShenandoahHeapRegion *r = heap->get_region(i);
767 if (r->is_empty_committed() && (r->empty_time() < shrink_before)) {
768 has_work = true;
769 break;
770 }
771 }
772
773 if (has_work) {
774 heap->entry_uncommit(shrink_before, shrink_until);
775 }
776 }
777
778 bool ShenandoahControlThread::is_explicit_gc(GCCause::Cause cause) const {
779 return GCCause::is_user_requested_gc(cause) ||
780 GCCause::is_serviceability_requested_gc(cause);
781 }
782
783 bool ShenandoahControlThread::is_implicit_gc(GCCause::Cause cause) const {
784 return !is_explicit_gc(cause) && cause != GCCause::_shenandoah_concurrent_gc;
785 }
786
787 void ShenandoahControlThread::request_gc(GCCause::Cause cause) {
788 assert(GCCause::is_user_requested_gc(cause) ||
789 GCCause::is_serviceability_requested_gc(cause) ||
790 cause == GCCause::_metadata_GC_clear_soft_refs ||
791 cause == GCCause::_codecache_GC_aggressive ||
792 cause == GCCause::_codecache_GC_threshold ||
793 cause == GCCause::_full_gc_alot ||
794 cause == GCCause::_wb_young_gc ||
795 cause == GCCause::_wb_full_gc ||
796 cause == GCCause::_wb_breakpoint ||
797 cause == GCCause::_scavenge_alot,
798 "only requested GCs here: %s", GCCause::to_string(cause));
799
800 if (is_explicit_gc(cause)) {
801 if (!DisableExplicitGC) {
802 handle_requested_gc(cause);
803 }
804 } else {
805 handle_requested_gc(cause);
806 }
807 }
808
809 bool ShenandoahControlThread::request_concurrent_gc(GenerationMode generation) {
810 if (_preemption_requested.is_set() || _gc_requested.is_set() || ShenandoahHeap::heap()->cancelled_gc()) {
811 // ignore subsequent requests from the heuristics
812 return false;
813 }
814
815 if (_mode == none) {
816 _requested_gc_cause = GCCause::_shenandoah_concurrent_gc;
817 _requested_generation = generation;
818 notify_control_thread();
819 MonitorLocker ml(&_regulator_lock, Mutex::_no_safepoint_check_flag);
820 ml.wait();
821 return true;
822 }
823
824 if (preempt_old_marking(generation)) {
825 log_info(gc)("Preempting old generation mark to allow %s GC.", generation_name(generation));
826 _requested_gc_cause = GCCause::_shenandoah_concurrent_gc;
827 _requested_generation = generation;
828 _preemption_requested.set();
829 ShenandoahHeap::heap()->cancel_gc(GCCause::_shenandoah_concurrent_gc);
830 notify_control_thread();
831
832 MonitorLocker ml(&_regulator_lock, Mutex::_no_safepoint_check_flag);
833 ml.wait();
834 return true;
835 }
836
837 return false;
838 }
839
840 void ShenandoahControlThread::notify_control_thread() {
841 MonitorLocker locker(&_control_lock, Mutex::_no_safepoint_check_flag);
842 _control_lock.notify();
843 }
844
845 bool ShenandoahControlThread::preempt_old_marking(GenerationMode generation) {
846 return generation == YOUNG && _allow_old_preemption.try_unset();
847 }
848
849 void ShenandoahControlThread::handle_requested_gc(GCCause::Cause cause) {
850 // Make sure we have at least one complete GC cycle before unblocking
851 // from the explicit GC request.
852 //
853 // This is especially important for weak references cleanup and/or native
854 // resources (e.g. DirectByteBuffers) machinery: when explicit GC request
855 // comes very late in the already running cycle, it would miss lots of new
856 // opportunities for cleanup that were made available before the caller
857 // requested the GC.
858
859 MonitorLocker ml(&_gc_waiters_lock);
860 size_t current_gc_id = get_gc_id();
861 size_t required_gc_id = current_gc_id + 1;
862 while (current_gc_id < required_gc_id) {
863 // Although setting gc request is under _gc_waiters_lock, but read side (run_service())
864 // does not take the lock. We need to enforce following order, so that read side sees
865 // latest requested gc cause when the flag is set.
866 _requested_gc_cause = cause;
867 _gc_requested.set();
868 notify_control_thread();
869 if (cause != GCCause::_wb_breakpoint) {
870 ml.wait();
871 }
872 current_gc_id = get_gc_id();
873 }
874 }
875
876 void ShenandoahControlThread::handle_alloc_failure(ShenandoahAllocRequest& req) {
877 ShenandoahHeap* heap = ShenandoahHeap::heap();
878
879 assert(current()->is_Java_thread(), "expect Java thread here");
880
881 if (try_set_alloc_failure_gc()) {
882 // Only report the first allocation failure
883 log_info(gc)("Failed to allocate %s, " SIZE_FORMAT "%s",
884 req.type_string(),
885 byte_size_in_proper_unit(req.size() * HeapWordSize), proper_unit_for_byte_size(req.size() * HeapWordSize));
886
887 // Now that alloc failure GC is scheduled, we can abort everything else
888 heap->cancel_gc(GCCause::_allocation_failure);
932 _do_counters_update.unset();
933 ShenandoahHeap::heap()->monitoring_support()->update_counters();
934 }
935 }
936
937 void ShenandoahControlThread::handle_force_counters_update() {
938 if (_force_counters_update.is_set()) {
939 _do_counters_update.unset(); // reset these too, we do update now!
940 ShenandoahHeap::heap()->monitoring_support()->update_counters();
941 }
942 }
943
944 void ShenandoahControlThread::notify_heap_changed() {
945 // This is called from allocation path, and thus should be fast.
946
947 // Update monitoring counters when we took a new region. This amortizes the
948 // update costs on slow path.
949 if (_do_counters_update.is_unset()) {
950 _do_counters_update.set();
951 }
952 }
953
954 void ShenandoahControlThread::pacing_notify_alloc(size_t words) {
955 assert(ShenandoahPacing, "should only call when pacing is enabled");
956 Atomic::add(&_allocs_seen, words, memory_order_relaxed);
957 }
958
959 void ShenandoahControlThread::set_forced_counters_update(bool value) {
960 _force_counters_update.set_cond(value);
961 }
962
963 void ShenandoahControlThread::reset_gc_id() {
964 Atomic::store(&_gc_id, (size_t)0);
965 }
966
967 void ShenandoahControlThread::update_gc_id() {
968 Atomic::inc(&_gc_id);
969 }
970
971 size_t ShenandoahControlThread::get_gc_id() {
972 return Atomic::load(&_gc_id);
973 }
974
975 void ShenandoahControlThread::start() {
976 create_and_start();
977 }
978
979 void ShenandoahControlThread::prepare_for_graceful_shutdown() {
980 _graceful_shutdown.set();
981 }
982
983 bool ShenandoahControlThread::in_graceful_shutdown() {
984 return _graceful_shutdown.is_set();
985 }
986
987 const char* ShenandoahControlThread::gc_mode_name(ShenandoahControlThread::GCMode mode) {
988 switch (mode) {
989 case none: return "idle";
990 case concurrent_normal: return "normal";
991 case stw_degenerated: return "degenerated";
992 case stw_full: return "full";
993 case servicing_old: return "old";
994 default: return "unknown";
995 }
996 }
997
998 void ShenandoahControlThread::set_gc_mode(ShenandoahControlThread::GCMode new_mode) {
999 if (_mode != new_mode) {
1000 log_info(gc)("Transition from: %s to: %s", gc_mode_name(_mode), gc_mode_name(new_mode));
1001 _mode = new_mode;
1002 MonitorLocker ml(&_regulator_lock, Mutex::_no_safepoint_check_flag);
1003 ml.notify_all();
1004 }
1005 }
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